Design Pattern Density Defined

Abstract: Design pattern density is a metric that measures how much of an object-oriented design can be understood and represented as instances of design patterns. Expert developers have long believed that a high design pattern density implies a high maturity of the design under inspection. This paper presents a quantifiable and observable definition of this metric. The metric is illustrated and qualitatively validated using four real-world case studies. We present several hypotheses of the metric’s meaning and their implications, including the one about design maturity. We propose that the design pattern density of a maturing framework has a fixed point and we show that if software design patterns make learning frameworks easier, a framework’s design pattern density is a measure of how much easier it will become.